Cellular Control | OCR A-Level Biology A (H420)
Cellular Control
- 62 questions
- 6 subtopics
- Module 6: Genetics, evolution and ecosystems
- Component 02 and Component 03
Cellular control opens Module 6, examined on Biological Diversity.
It covers the three kinds of gene mutation and their effects, the lac operon as a model of gene regulation, transcription factors and splicing, the homeobox and Hox genes that lay out a body plan, apoptosis, and how mutation leads to cancer.
Sample questions from Cellular Control
Answer each one closed book first, then open the answer.
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Gene mutations and their effects
Why might a single nucleotide substitution have no effect on the protein produced?
Show the answer
It may result in a silent mutation if the new codon still codes for the same amino acid due to the degeneracy of the genetic code. -
Gene mutations and their effects
Under what circumstances could a gene mutation be considered beneficial?
Show the answer
When the altered protein confers a selective advantage to the organism. -
The lac operon
What does the lacA gene encode in the lac operon?
Show the answer
It is a structural gene that codes for transacetylase, involved in lactose metabolism. -
The lac operon
What happens at the lac operon when lactose is absent?
Show the answer
The repressor protein binds to the operator and prevents RNA polymerase from transcribing the structural genes. -
Transcription factors and post-transcriptional control
What is post-transcriptional control?
Show the answer
The editing of primary mRNA (pre-mRNA) before it leaves the nucleus. -
Transcription factors and post-transcriptional control
How does alternative splicing increase protein diversity?
Show the answer
Different combinations of exons can be joined, producing different mature mRNA molecules and thus different proteins from a single gene. -
Homeobox and Hox genes
Why are homeobox genes highly conserved across different species?
Show the answer
They have essential functions that have been maintained by natural selection. -
Homeobox and Hox genes
What aspects of body organisation do Hox genes determine?
Show the answer
They determine the anterior-posterior axis and specify which structures develop in each segment of the body.
The 6 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Gene mutations and their effects | Substitution, insertion and deletion, missense and nonsense mutations, why a frameshift is so damaging, and when a mutation is neutral, harmful or beneficial. | 10 |
| The lac operon | The lacZ, lacY and lacA genes, the promoter, the operator and the regulatory gene, and what changes at the operon when lactose is present. | 10 |
| Transcription factors and post-transcriptional control | Transcription factors as activators and repressors, introns, exons and splicing, alternative splicing, and post-translational control through cyclic AMP. | 11 |
| Homeobox and Hox genes | What the homeobox encodes and why it is so highly conserved across species, and how Hox genes are arranged and what their mutation can produce. | 9 |
| Mitosis and apoptosis | Why both are needed during development, and the shrinking, chromatin condensation, DNA breakdown and apoptotic bodies of programmed cell death. | 9 |
| Oncogenes, tumour suppressor genes and cancer | The normal role of proto-oncogenes and tumour suppressor genes in the cell cycle, and what happens to that control when either one is mutated. | 13 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby sections
OCR A-Level Biology A Active Recall Guide
Every section, not just this one. 1,833 questions with their answers.